carry on muso - interesting stuff.

That's right, Mozz, and by the way I was just joking . Feel free to jump in any time. 

Grendel raised an interesting point about volcanoes. Let's examine that.

If we look at the graph of mean global temperature, we can see a small blip about 18 months after the eruption of Mt Pinatabo in 1991. The interesting thing is that the blip is in the negative, and that's because explosive stratospheric volcanoes like Mt Pinatabo release primarily dust and sulphur dioxide which have an overall cooling effect. You can discount virtually all volcanoes beneath the sea, because almost without exception, they are basaltic, and have very little gas evolution.  The ones that make the difference are very large stratospheric volcanoes.

Gases and dust from stratospheric volcanoes are carried up into the stratosphere (12 to 15 km above the ground). There, because this is well above the clouds and rain of the troposphere, the sulphates can hang around for a long time (sometimes a few years).

Prior to that El Chichon (Mexico, in 1982), Mt. Agung (Indonesia, 1963), Santa Maria (Guatemala, 1902) and Krakatoa (Indonesia, 1883) all had noticeable cooling effects. There was quite a large volcano in Chile last year, but that is not expected to have any significant cooling effect. The main reason is that it was too far from the equator, and was too small to have any appreciable effect.

That's an extraordinary statement Soren. On what basis do you say that?

muso wrote on Oct 16^th, 2008 at 8:22pm:



1. SCience requires that a hypothesis be falsifiable. What would, in other words, be accepted as proof that global warming is NOT man made?

2. A scientific experiment has to be conducted repeatedly to test the falsfiable hypothesis. This requires controls as well as reruns. There is no control cohort or group or site to test the global warming hypothesis against. there are no reruns - we don't live long enough. We do not have experimental data from long enough and we have only one cohort - this earth.

2.a  Climate is complex beyond our present grasp. It is influenced by far too many factors. Tthe conceivable experiments would neeed to be controlled for a vast amount of variables we cannot, in fact account for, let alone control.

3.  Whatever models we may construct, they are only partial maps of this complex phenomenon. To treat the partial models, and whatever may be surmised from them, as proof or full explanations of the whole climate phenomenon is absurd and scientifically untenable.

4. We cannot make accurate predictions for the weather for even for local areas byond a day or two, and even then it is inaccuare guesses in significant

Soren, if we eliminated our CO2 emissions and it had no impact on climate change, that might disprove AGW.

AGW is not a single theory. It is comprised of many scientific theories, all of which are far more easy to falsify.

Ultimately the political response comes down to risk management, not science. It is important not to confuse the two approaches and demand a scientific approach to making political decisions. One approach would lead you to conduct the grand experiment, the other to avoid it.

I don't have a problem if peeople decide to cut CO2 emissions because it might be the cause, as long as they undertsand that it might not be. I am all for irsk management. That would be acting on a sentiment, like insurance.
But it is not scientific proof of anything. It's a guess. It might be prudent like not walking under a ladder.

I would be interested if someone could engage with the falsifiability question. What woul be acceptable proof, in the current thinking and hypothetical framework, that climate  change is NOT man made?

Sprint,

Every last Climate Scientist knows that there are natural cycles. To say that they overlook that is total nonsense, but certain people are trying to muddy the waters by claiming that the huge increases in CO2 over the late 20th century and early 21st century are the same ballgame, whereas they are not!

The main driver for climate is the sun. We know that the Earth has natural cyclical changes in its orbit (Milankovitch cycles) that resulted in a cycle of ice ages and interglacials every 130,000 years. Prior to about 1 million years ago, the period changed, but that's not relevant to this discussion. The predicted changes in orbital forcing suggest that the next glacial period would begin in around 50,000 years.

Apart from orbital forcing, the other sigificant factor is that of small fluctuations in the solar irradiance. We can measure that today using satellites. There was a blip around the 1940's which caused the slight increase in temperature. We'd know if there was another blip, but it's really the last thing we'd need right now. There are ways that we can extrapolate Solar irradiance back through the ages. The techniques match pretty well with direct satellite data. An  example is Beryllium proxy data. These proxies are not perfect, so that's why we use different proxies as a check.

I'm sure you've seen graphs like this before. Sorry I don't have a better example, but work is catching up with me, and this will be my last post probably until next week. The important thing is the scale. You're talking tens of thousands of years as against years. The rate of increase in the past 150 years is totally unprecedented. The CO2 levels are higher than anything we've seen for the last 50 million years and the rate of increase matches suspiciously well with the rate of carbon emissions from Anthropogenic sources.

We'll take a look at the Global Carbon Balance next week some time. To understand what's going on, you really need to study that with an open mind.

It's a question of approach. My approach has been to examine the data and decide what is the most likely scenario, and once you do that, It becomes as obvious as canine gonads. The anthropogenic signature is not even subtle.

Those who seek proof are obfuscating, pure and simple. Of course you can't get hard rigorous proof. It's like running a chemical process. You run it according to the data you get from the process. If you were to agonize over every single variable point, the chemical plant would come to a screaming halt pretty quickly. You'd get nowhere.

The Earth's troposphere and hydrosphere together has become a huge chemical process. Whether we like it or not, we (humans) are driving it. It will be interesting to see what happens to the CO2 levels if there is a long economic depression.  It might mean that alternative energy would go out the window as too expensive, but emissions would almost certainly go down during the period of the depression.

If the economic downturn goes on for a few years, we even might see its mark on the Mauna Loa station monthly CO2 emissions.  

Soren wrote on Oct 16^th, 2008 at 10:00pm:


How does 'by far the most likely explanation' sound to you?

If you tread on something on the pavement and it's brown and it smells bad and it's dog turd shaped, you act on the most likely explanation. Maybe there is a possibility that it's chocolate. Can you prove otherwise?  No?